Null poinnter exception with array in C++

Question

I tried to learn basics for C++. Now I'm trying to figure out the arrays. But then i running this small program my IDE raise the null pointer exception.I didn't understand why this happend.

include <iostream>

using namespace std;

int main(){
int[] arr = {1, 2, 3};
for(int i=0; i < 4; i++){
  cout << arr[i] << endl;
}
exit 0;
}

I searched for answers on google about null pointer exception. I understand what it is, but don't understastand why it raised in my program. My array has 3 items, so the i<4 statement is correct in my opinion

Answer 1

The array has three elements, but you are trying to access the fourth one on the last iteration. The condition in the for loop is wrong. (Note: you can calculate the number of elements using sizeof arr / sizeof *arr or std::size(arr) , since C++ 17.)

int arr[] = {1, 2, 3}; 
for (int i = 0; i < 3; i++){
  std::cout << arr[i] << '\n';
}

To avoid this sort of issue altogether, use a range-based for loop .

for (const int& x : arr) {
    std::cout << x << '\n';
}